An existing material used for manufacturing short wave-infrared focal-plane arrays (SWIR FPA) is InGaAs, which is expensive and incompatible with silicon processing. Silicon-germanium strained-layer superlattice structure (Si:Ge SLS) is used as an alternative. However, growing uniform single-crystal germanium on silicon substrate is a challenge due to silicon and germanium lattice mismatch. Growing an ultrathin layer of germanium on top of a layer of silicon-germanium, or alternating layers of silicon-germanium with varying silicon content, with abrupt transitions for making hundreds of pairs of layers of strained-layer superlattice is another challenge. What is needed is a method for growing silicon-germanium strained-layer superlattice structure on silicon substrates that overcomes silicon and germanium lattice mismatch and provides an ultrathin layer of germanium on top of a layer of silicon-germanium with abrupt layer transitions for making hundreds of pairs of layers of superlattice that is which is less expensive and compatible with silicon processing.